1. Field of the Invention
The present invention relates to backlight modules, particularly, to backlight modules used in the field of liquid crystal displays (LCDs).
2. Description of Related Art
LCDs are widely used in electronic products. In an LCD device, liquid crystal is a substance that does not itself radiate light Instead, the liquid crystal receives light from a light source to display images and datas.
A conventional LCD device includes a light source, a light guide plate, a reflector, a scattering plate, and a prism system. The light source is commonly called a backlight source, since it is usually configured behind a liquid crystal panel of the liquid crystal display. A combination of all components behind the liquid crystal panel, including the light source, is generally named a backlight module. Generally, backlight modules can be classified as an edge type backlight module or as a direct type backlight modules. In the edge type backlight module, the light source is positioned adjacent to a thin edge of the light guide plate. In the direct type backlight module, the light source is positioned behind a light guide plate.
Typically, cold cathode fluorescent lamps (CCFLs) and light emitting diodes (LEDs) are employed as light sources in backlight modules. However, backlight modules employing CCFLs have the disadvantages of high-energy consumption, low uniformity of brightness, poor purity of white light, and high cost. In addition, after being used for a period of time, the brightness of CCFLs tend to become degraded, and the color of the light output is apt to shift. Accordingly, the light sources of the CCFLs generally cannot satisfy the high quality requirements of certain high-end liquid crystal displays.
Compared to CCFL light sources, light emitting diodes (LEDs) have many advantages, such as high brightness, low energy consumption, long service life, and so on. In particular, high-power LEDs are considered more suitable for certain high-end liquid crystal displays. Light-emitting diodes are reported in an article by Ya-Ju Lee entitled “High Brightness GaN-Based Light-Emitting Diodes” (Display Technology, Journal of Volume 3, Issue 2, June 2007, P 118-125), which is incorporated herein by reference.
However, each of the LEDs generally has a limited range of light emission angles. As a result, a number of dark regions are formed in areas of the light guide plate, these dark regions are generally between every two adjacent LEDs, and a number of bright regions are formed in areas of the light guide plate corresponding to each of the LEDs. That is, the backlight module has non-uniform brightness.
What is needed, therefore, is a backlight module with uniformity of output light.